Air bag deployment has created many problems including providing a closed opening which is covered by either a door or a weakened section in the housing for the air bag which will separate from the housing to provide a path for deployment of an air bag into the passenger compartment as it is inflated.
Some of the prior art pads or covers for air bag devices are not soft and do not match or conform to the styling and aesthetic requirements of an associated interior trim product in which the air bag restraint system is housed. Such covers are often formed from injection molded thermoplastic elastomers or thermoplastic olefin which are suitable for midmount locations such as on the front vertical surface of an instrument panel which locations are not subject to radiant heating by sunlight directed through a front windshield of a vehicle. Such covers do not always perform satisfactorily if exposed to direct radiant heating, e.g., when located on the upper surface of an instrument panel or dashboard.
Other prior art pads or covers include a foamed interior which provides a soft feel and an outer skin which can be aesthetically matched to the material of the outer surface of an interior product which houses the air bag restraint system.
Examples of such prior art doors are shown in U.S. Pat. No. 3,708,179 which discloses mid-mounted doors formed of a layer of urethane foam and an outer cover of a plastisol skin material. The '179 structure is supported on a pair of spaced hinge pins for movement outwardly of the front vertical face of an instrument panel so as to permit deployment of an air bag into the passenger compartment at the passenger side of the front seat.
U.S. Pat. Nos. 4,946,653 and 4,893,833 disclose door configurations for closing a upper mount configuration wherein the door is inserted within an upper surface of an instrument panel and moved upwardly toward the windshield of the vehicle when the air bag is deployed.
In the construction of doors with soft foam inserts or substrates, a preformed outer skin or shell member formed by casting vinyl particles on a heated mold surface is placed in a female cavity of a foam mold of the type shown in U.S. Pat. Nos. 4,734,720 and 4,743,188 which are commonly assigned to the assignee of the present application, and which are incorporated herein by reference. A first substrate member is supported at construction holes therein on the lid of the mold which closes to form a mold space between the substrate and the preload vinyl skin. The substrate on the lid can also include a port through which foam precursors are directed into the mold space for reaction therein to form a cellular foam material that is soft to the feel. The resultant structure is removed from the foam mold and includes a vinyl skin which can be colored and grained to match the aesthetic appearance of the outer vinyl surface of an interior trim product such as an instrument panel having a upper opening therein for the deployment of an air bag.
Such doors have included a single substrate with openings therein through which foam escapes during the foaming process. In the past it has been necessary to clean the part to remove escaped foam and cover the foam openings so that the door is suitable for shipping and for use at final assembly. At final assembly, the door is connected either to the reinforcing insert in an interior trim product or to the canister of an air bag restraint system as determined by the ultimate original equipment manufacturer of such door and interior trim products.
Another problem with such doors has arisen since its substrate must meet several requirements including support of the product during the mold process and support of the door for hold-down and hinged connection to an associated part such as a canister housing or a reinforcing insert within the interior trim product.
The use of a door substrate for such purpose can impose higher stresses in the foam and vinyl of the door during air bag deployment leading to fragmentation or tearing thereof so as to produce debris problems of the kind discussed in U.S. Pat. No. 4,964,653 which is commonly assigned to the same assignee of the present application.